1. Field of the Invention
The present invention relates to a method and an apparatus for sensing a blood sample contained in a sample container.
2. Description of the Related Art
In order to separate blood into a serum and a clot accurately using a centrifuge or the like, a test tube 1 containing a silicon-separating medium B is used. If the blood in the test tube 1 is centrifuged, it is separated into a serum A and a clot C by the silicon-separating medium B, and air D is sealed in between the serum A and a stopper 2. A blood sample is thus obtained in the test tube 1 as shown in FIG. 1.
When the above blood sample is processed to aliquot the serum A in the test tube 1 by sticking a nozzle of an aliquot/pipette instrument into the stopper 2 to reach the serum A, it is required to sense the following: separation positions of the blood sample, i.e., position e of separation between air D and serum A, position f of separation between serum A and silicon-separating medium B and position g of separation between clot C and silicon-separating medium B, separation ranges of height d of air D, height a of serum A and height b of silicon-separating medium B, and height h of stopper 2.
The air D, serum A and silicon-separating medium B differ in height and their heights d, a, and b vary with the amount of the blood sample in the test tube 1. If these heights are not sensed accurately, the following problems will occur: the nozzle of the aliquot/pipette instrument contacts the silicon-separating medium B and sucks it up, and the nozzle stops in the middle position of the serum A to leave the serum A on the top of the silicon-separating medium B.
A blood sample sensing apparatus as described above is disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2002-323479. In this apparatus, a sensing coil is fitted into a test tube 1 that contains a serum A and a clot C separated by a silicon-separating medium B. The sensing coil moves relative to the test tube 1 while being supplied with a measurement signal having a given frequency. A position between the serum A and clot C is sensed based on the level variations of the measurement signal.
The sensing apparatus disclosed in the above Publication adopts a magnetic sensing means using a sensing coil. It is thus difficult to sense respective separation positions of a blood sample, respective separation ranges of height d of air D, height a of serum A and height b of silicon-separating medium B, and height h of stopper 2. The above sensing apparatus also has problems in that its configuration is complicated and its costs become high.